To make it more difficult to create high quality counterfeit banknotes, genuine banknotes include a variety of security features. Some of these security features can be detected using imaging sensors, such as a fluorescent security feature (which responds to an ultra-violet light source), an infra-red security feature (which produces a characteristic response to an infra-red light source), and the like. However, some types of security feature cannot be detected using an imaging sensor. One such security feature is magnetic ink, which is used to print some parts of a banknote.
It would be desirable to be able to detect a counterfeit banknote (or other counterfeit media item) using magnetic sensors either instead of, or in addition to, using imaging sensors.